The present invention relates to a blowing device that suctions gas from a suction inlet of a blowing portion and exhausts the gas from an exhaust outlet, to a holder that configures a part of the blowing device, to a sheet discharge device equipped with the blowing device near a sheet discharge port to a sheet discharge tray, and to an electrophotographic image forming apparatus equipped with the blowing device between a fixing portion and a sheet discharge portion.
An electrophotographic image forming apparatus, after heating and pressurizing at a fixing portion a sheet of paper bearing a toner image transferred to the sheet of paper, discharges the sheet of paper to a sheet discharge tray. During continuous image formation with respect to a large number of sheets of paper, the large number of sheets of paper heated at the fixing portion are stacked and stored on the sheet discharge tray, so that each of the sheets of paper is held between other upper and lower sheets of paper on the sheet discharge tray and is likely to be left in a high temperature.
In particular, in a so called in-body sheet discharge type image forming apparatus in which a sheet discharge tray is arranged between an image reading portion and a sheet storage portion, heat dissipation of the sheets of paper is insufficient, and, during continuous image formation, a large number of sheets of paper are stacked and stored on the sheet discharge tray while being still in a high temperature. As a result, due to addition of the weight of upper sheets of paper, a toner image is retransferred onto a sheet of paper of which the upper surface contacts the sheet of paper bearing the toner image, which causes degradation of image quality and stain of the sheet of paper.
In view of the foregoing, some conventional image forming apparatuses include a blowing device arranged at a discharge port to a sheet discharge tray and are configured to cool the sheets of paper discharged to the sheet discharge tray by applying air to the sheets of paper. The sheets of paper heated at the fixing portion are cooled down by blowing air before the sheets of paper are stored on the sheet discharge tray, and a large number of sheets of paper are prevented during continuous image formation from being stacked and stored on the sheet discharge tray while being still in a high temperature, which thus can prevent degradation of image quality and stain of a sheet of paper.
In the image forming apparatus, a reduction in size has been strongly requested, a space between the fixing portion and the sheet discharge port is narrow, and therefore a blowing device needs to be configured in a small size. Thus, for example, in a configuration disclosed in Japanese Patent Laid-Open Publication No. 2000-297783, a sirocco fan is used, the sirocco fan being equipped with a cylindrical casing; and a dish including a number of fins that are annularly raised on the peripheral edge portion of the disk. The sirocco fan, by rotation of the disk in the casing, discharges gas suctioned into the casing in the axial direction of the casing, from an exhaust outlet formed on the peripheral surface of the casing to the outside. The lengths of the casing and the fin in the axial direction are formed short and a motor that supplies a rotational force to the disk is arranged inside the fin, and a blowing device can thereby be formed small.
However, since such a blowing device applied to an image forming apparatus for the purpose of cooling of a sheet of paper to be discharged to a sheet discharge tray is arranged close to a high-temperature fixing portion, the blowing device itself is affected by the heat from the fixing portion, which makes the cooling of a sheet of paper insufficient and causes modification or breakage of each portion, failure of a motor, or the like. In particular, if a motor as a heat generating source as well is arranged inside a fin, an internal temperature will further easily rise during continuous use.
The occurrence of these problems such as rise in blowing temperature, breakage, and failure is not limited to a case in which a blowing device is applied to an image forming apparatus but a general problem in the blowing device used in a comparatively high temperature environment.
An object of the present invention is to provide a blowing device capable of suppressing temperature rise in the blowing device and preventing occurrence of rise in blowing temperature, breakage, and the like, by leading part of the gas exhausted from the blowing device to the inside of the blowing device. Another object of the present invention is to provide a sheet discharge device capable of sufficiently cooling a sheet of paper discharged to a sheet discharge tray by applying this blowing device, and to provide an image forming apparatus capable of thereby continuously preventing degradation of image quality or stain of a sheet of paper during continuous image formation.